Serpentine antenna mounted on a rotatable capacitive coupler

ABSTRACT

This disclosure teaches an antenna including a conductor disposed in a serpentine arrangement defined by a plurality of undulations, wherein the amplitude or size of the undulations determines the directivity of the antenna, and wherein the undulations function to cancel mutual inductance parameters of the antenna while increasing the capacitive reactance thereof, to yield broadband characteristics. The antenna can take a variety of shapes, as for example the undulations may all fall entirely in a common plane and generally define a circle, a square, or an ellipse, etc.; or, such undulations may be arranged to form a ring or other three-dimensional object. The said shape of the antenna and its disposition with the earth&#39;&#39;s surface also contribute to the directivity of the antenna.

. Elnited States Patent [19] Root [ Feb. 13, 1973 [76] Inventor: John J.Root, 3875 Waldo Avenue, Bronx, N.Y. 10463 [22] Filed: March 22, 1971 I[21] Appl. No.: 126,448

[52] U.S. Cl. ..343/74l, 343/806, 343/882 [51] Int. Cl. ..H0lq 9/16 [58]Field of Search ..343/74l 744, 748, 802, 806,

Primary Examiner-Eli Lieberman Attorney-Charles E. Baxley, Frank M.Nolan and Thomas E. Tate [57] ABSTRACT This disclosure teaches anantenna including a conductor disposed in a serpentine arrangementdefined by a plurality of undulations, wherein the amplitude or size ofthe undulations determines the directivity of the antenna, and whereinthe undulations function to cancel mutual inductance parameters of theantenna while increasing the capacitive reactance thereof, to yieldbroadband characteristics. The antenna can take a variety of shapes, asfor example the undulations may all fall entirely in a common plane andgenerally define a circle, a square, or an ellipse, etc.; or, suchundulations may be arranged to form a ring or other three-dimensionalobject. The said shape of the antenna and its disposition with theearths surface also contribute to the directivity of the antenna.

10 Claims, 8 Drawing Figures PATENTED FEB] 5197s SHEET 10F 2 JOHN J.ROOT FIG.

PATENTEDFEBI 3l973 3,

snsn 2 or 2 INVENTOR.

JOHN J. ROOT Attorney BACKGROUND OF THE INVENTION A conventional methodof fabricating a broadband antenna is to couple together a plurality ofhighly-selective antennae. For example, a conventional televisionreceiving antenna comprises a plurality of dipoles coupled together on aboom for connection to the television receiver. However, dipole antennaewhich are disposed adjacent each other are subject to an interactionwhich changes their individual characteristics in ways which are almostimpossible to predict. Accordingly, it is usually necessary toexperiment with antennae configurations in an effort to arrive at properrelationships between length and spacing of elements. A further problemof such conventional antennae is that they are highly directional andmust be pointed towards the transmission source for good reception.

A principal object of this invention is to provide a broadband antennawhich alleviates the coupling problems of conventional antennae, andwhich lends itself to a plurality of similar configurations providingwidely varying directivity qualities.

SUMMARY OF THE INVENTION In accordance with the invention, there isprovided a broadband transmit/receive antennaincluding a conductorarranged in a serpentine configuration to provide a plurality of loopportions or undulations. The

changing direction of the antenna element cancels mutual inductancebetween the undulations, and the capacitive reactance of the antenna isincreased by increasing the number of undulations thereof. Thus, such anincrease in the number of undulations causes an unbalanced reactancecharacteristic and a resultant increase in radiation resistance of theantenna system, thereby providing the antenna with a broadband frequencyresponse.

The directivity of the antenna is controlled by the relative dispositionof the individual undulations in the serpentine arrangement. Forexample, if the undulations are arranged in a common plane, then thedirectivity can be controlled by the positioning of the plane defined bythe antenna. In this respect, the undulations can be arranged to form acircle, a diamond shape, a square or any other geometric configuration.Then, in another embodiment, the undulations can be formed in a band, orin the form of a truncated cone, to control the directivity of theantenna.

' The directivity is also effected by the size or amplitude of eachundulationin the serpentine arrangement. For example, if theundulationslie in a common plane, and if such amplitude defines one wavelength atthe lowest desired frequency of the broadband antenna, then thedirectivity of theantenna is normal to the common plane in which theundulations lie. Alternatively, if the amplitude is arranged at one-halfwavelength of the lowest frequency, then thedirectivity of the antennais to the edges of the plane in whichthe element lies.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawing illustratesvarious modifications of a preferred embodiment of theinvention. In suchdrawing:

FIG. 1 is an elevational view of a broadband antenna according to theinvention;

FIG. 2 is an enlarged view of a support portion of the antenna of FIG.1, with sections broken away for clari- FIG. 3 is a sectional view takenalong the line 3-3 of FIG. 2; and

FIGS. 4-7 are views similar to FIG. 1, but showing antennae havingdifferent profiles than that illustrated in FIG. 1.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT As illustrated in thedrawings, all of the modifications of the invention include an antennaelement defining a serpentine arrangement of individual undulations. Theundulations in each modification have the same size, and as describedbelow, the relative disposition and size of the undulations determinesthe directivity of the antenna, while the number of undulationsdetermines its broadband response.

In a rotational antenna assembly 2 according to the invention, asillustrated in FIGS. 1-3, an antenna element portion 4 is formed by acontinuous serpentine arrangement of antenna tubing 6, and is mounted ona pedestal assembly 10. The serpentine arrangement of the tubing 6 isformed by outer and inner bends 6a and 6b which define peaks and valleysof the loop portions or undulations, and which follow a generallycircular path. A sleeve hollow member composed of portions 20, 22, 24 isheld in an upright position with a straight portion 6e of the tubing byspaced upper and lower discs 8 and 12. One end 60 of the tubing ismounted on the upper end of the sleeve portion adjacent a bent portion6d of the tubing and the portion 6d defines the transition between thestraight portion 6e and the serpentine portion of the tubing 6. Thelower disc 12 is fixed to a rotatable support plate 14, which in turn,rotatably rests-by means of a conventional ball bearing 14b'on anelectrical connector block 16 fixed to a base member 18.

As shown, the element 4 and'sleeve portions 20, 22 and 24 are fixedtogether and torplate 14 for rotation with respect to the base memberand connector block 18 and 16, which in turn are fixed together as by ascrew 18a. That is, the end 6c of the tubing 6 passes into a recess 8ain the disc 8, wherein it is electrically connected by a member 22a tothe upper end of conductive sleeve portion 22.'The conductive sleevepor-- the straight portion 6e of the tubing passes through an opening 8bin the insulative disc 8, and is fixed at its lowermost end within anopening 12a in the lower disc 12, which in turn is fixed to the plate 14as by a screw 14a. Thus, the tubing end 6c and the straight portion 6eof the tubing are both fixedly interconnected with the plate 14 forrotation therewith.

A length of twin-lead cable 34 is provided and has one conductorconnected directly to the metal conductor block 16 as at 16c, and-itsother conductor mounted insulatively on the block 16 as at and 16b. Aninsulative tube 26 extends upwardly from the base member pled, directly,to the sleeve portion 24, which in turn is electrically coupled,indirectly, to the conductive sleeve 30 by the coaxial dispositiontherebetween.

An insulated conductor lead 32 is connected to the insulated mountingpoint 16a, 16b between the block 16 and the other conductor of thetwin-lead cable 34, and-the lead 32 passes upward through the insulativetube 26 for electrical connection to the upper conductive tube 28 as at280. Thus, the tube 28 and sleeve portion 22 provide an indirectelectrical coupling along their coaxial extent to complete the antennacircuit.

Accordingly, the antenna assembly 2 provides a rotational antennaelement 4 to facilitate adjustments in the directivity of the antenna.

The serpentine configuration functions to cancel the mutualinductance'of the element 4 with the result that the capacitivereactance of the element has an increasing relationship with respect toan increase in thenumber of undulations. That is, a reactance imbalanceoccurs due to the decrease in inductance.

- In the antennaillustrated in FIG. 1, all of the undulations of thetubing 6 are disposed in a common vertical plane, and are arranged in acircle, with the connecting leads of cable 34 being for coupling theantenna to a transmitting and/or receiving device. Both the antennaelement of FIG. 1 and that of FIG. 4 provide for horizontalpolarizationof the antenna pattern, and as illustrated, the device ofFIG. 4 differs from FIG. 1 only in the arrangement of undulations. Thatis, in FIG. 4, the antenna element forms an elongated oval shape 36which provides the same broadband qualities and general directivity ofthe device of FIG. 1.

The various embodiments disclosed herein have been tested and havebeen'found to provide, for example, a frequency response from 50 MHz to890 MHz, whereby 50 MHz becomes the lowest frequency to be operativelyapplied to the antenna. Also, conventional coupling to the transmitteror receiver device is possible, as by stacking coupling or, as describedabove, by-

transmission lines to rotary devices.

In the antenna, of FIG. 5, the undulations are arranged to form a band38, wherein such undulations are defined axially of the band and advancecircumferentially thereof. Again, in the modification of FIG. 5, theantenna pattern is polarized horizontally and has characteristics whichare much the same as the antennae of FIGS. 1 and 4. In these threeembodiments it has been found that the size or amplitude of eachundulation, as indicated at reference numeral 40 in FIGS. 4 and 5 whichdesignates the distance between peak and valley portions of theundulations in each of those views, has' an effect'on the directivity ofthe device, according to the following relationship: if the amplitude 40is equal to one wavelength of the lowest frequency to .be transmitted orreceived, then the antenna will have a pattern extending in opposingdirections normal to a vertical plane through each undulation; and, ifthe undulation amplitudes define one-half wavelength of the lowestfrequency, the directivity of the device changes so that it projectsfrom the edges of the antenof FIGS. 1 and 5, respectively, wherein suchantennae are identical except for the disposition of their principalplanes; and, as shown, FIGS. 6a and 6b illustrate antennae, formed asbands 42 and 44 respectively, which are disposed horizontally ascompared to the vertically disposed antennae of FIGS. 1 and 5.

Another modification as illustrated in FIG. 7, defines an antennaelement which takes the shape of a truncated cone 46, wherein theundulations of the serpentine arrangement are disposed along the sidewalls of the cone. The directivity of the antenna of FIG. 7 is along theaxis of the cone, and in the direction of the vertex thereof. Again, thebroadband qualities of the device increase with an increase in thenumber of undulations.

Iclaim:

1. A broadband transmit/receive antenna comprising:

an antenna element having two ends and having between said two ends acontinuous serpentine configuration defined by a plurality of seriallyconnected together loop portions each orientated relative to itsimmediate adjacent loop portions to effectively cancel out mutualinductance occurring therebetween during use of the antenna;

support means for rotatably supporting said antenna element;

a pair of terminals connected to said support means and connectable todevices for transmitting and receiving electromagnetic energy during useof the antenna;

and means at.least partially disposed interiorly of said support meansfor capacitively connecting each end of said antenna element torespective ones of said terminals.

2. A broadband transmit/receive antenna as set forth in claim 1, inwhich said plurality of loop portions comprise means defining a directrelationship between the capacitive reactance of said antenna elementand the number of said loop portions. I

3. A broadband transmit/receive antenna as set forth in claim 1, inwhich all said loop portions lie'in a common plane. I

4. A broadband transmit/receive antenna as set forth in claim 3, inwhich said'plurality of loop portions comprise means defining an antennadirectivity extending normal to said common plane when said loopportions are of equal size and are equal to one wavelength of the lowestfrequency to be applied to said antenna, and said directivity is in saidcommon plane when said loopportions are of equal size and are equal toone-half wavelength of said lowest frequency.

5. A broadband transmit/receive antenna as set forth in claim 1, inwhich each said loop portion has a peak portion and a valley portion,and wherein each said peak portion lies in a first plane and each saidvalley portion lies in a second plane extending parallel to'said firstplane.

FIGS. 6a and 6b show modifications or the antennae 6. A broadbandtransmit/receive antenna as set forth in claim 5, in which saidplurality of loop portions comprise means defining an antennadirectivity extending normal to said first and second planes when saidloop portions are of equal size and are equal to one wavelength of thelowest frequency to be applied to said antenna, and said directivity isin a plane parallel to said first and second planes when said loopportions are of equal size and equal to one-half wavelength of saidlowest frequency.

7. A broadband transmit/receive antenna as set forth in claim 5, inwhich said plurality of loop portions form a hollow truncated conehaving major and minor diameters, wherein said first plane is disposedat the minor diameter of said truncated cone and said second plane isdisposed at the major diameter of said truncated cone, and wherein saidplurality of loop portions comprise means defining an antennadirectivity which is in a direction projecting outward from said firstplane.

8. A broadband transmit/receive antenna as set forth in Claim 1, whereinsaid support means comprises a base member, an insulative sleeve, firstand second conductive sleeve portions fixed on said insulative sleeve inaxially spaced-apart relationship, means rotationally interconnectingsaid insulative sleeve with said base member, conductive means forelectrically interconnecting one end of said antenna element to saidfirst conductive sleeve portion and the other end of said element tosaid second conductive sleeve portion, first and second conductiveterminals fixedly interconnected and means connecting said first andsecond conductive terminals to said first and second tubular members,respectively.

9. A broadband transmit/receive antenna as set forth in Claim 1; whereinsaid support means comprises a base member having connected thereto saidpair of terminals, an electrically insulated tube connected to andextending outwardly from said base member and having around the exteriorthereof a pair of peripherally extending and axially spaced-apartelectrically conductive portions,

a support plate having means therein defining an said antenna element torespective ones of said electrically conductivetportions of said hollowmember and electrically connecting said pair of terminals to respectiveones of said electrically conductive portions of said tube, whereby saidantenna element may be angularly displaced to vary the antennadirectivity. 10. A broadband transmit/receive antenna as set forth inclaim 9;

wherein said electrically conductive portions of said tube and hollowmember comprise annular sleeves connected to said tube and hollowmember.

1. A broadband transmit/receive antenna comprising: an antenna elementhaving two ends and having between said two ends a continuous serpentineconfiguration defined by a plurality of serially connected together loopportions each orientated relative to its immediate adjacent loopportions to effectively cancel out mutual inductance occurringtherebetween during use of the antenna; support means for rotatablysupporting said antenna element; a pair of terminals connected to saidsupport means and connectable to devices for transmitting and receivingelectromagnetic energy during use of the antenna; and means at leastpartially disposed interiorly of said support means for capacitivelyconnecting each end of said antenna element to respective ones of saidterminals.
 1. A broadband transmit/receive antenna comprising: anantenna element having two ends and having between said two ends acontinuous serpentine configuration defined by a plurality of seriallyconnected together loop portions each orientated relative to itsimmediate adjacent loop portions to effectively cancel out mutualinductance occurring therebetween during use of the antenna; supportmeans for rotatably supporting said antenna element; a pair of terminalsconnected to said support means and connectable to devices fortransmitting and receiving electromagnetic energy during use of theantenna; and means at least partially disposed interiorly of saidsupport means for capacitively connecting each end of said antennaelement to respective ones of said terminals.
 2. A broadbandtransmit/receive antenna as set forth in claim 1, in which saidplurality of loop portions comprise means defining a direct relationshipbetween the capacitive reactance of said antenna element and the numberof said loop portions.
 3. A broadband transmit/receive antenna as setforth in claim 1, in which all said loop portions lie in a common plane.4. A broadband transmit/receive antenna as set forth in claim 3, inwhich said plurality of loop portions comprise means defining an antennadirectivity extending normal to said common plane when said loopportions are of equal size and are equal to one wavelength of the lowestfrequency to be applied to said antenna, and said directivity is in saidcommon plane when said loop-portions are of equal size and are equal toone-half wavelength of said lowest frequency.
 5. A broadbandtransmit/receive antenna as set forth in claim 1, in which each saidloop portion has a peak portion and a valley portion, and wherein eachsaid peak portion lies in a first plane and each said valley portionlies in a second plane extending parallel to said first plane.
 6. Abroadband transmit/receive antenna as set forth in claim 5, in whichsaid plurality of loop portions comprise means defining an antennadirectivity extending normal to said first and second planes when saidloop portions are of equal size and are equal to one wavelength of thelowest frequency to be applied to said antenna, and said directivity isin a plane parallel to said first and second planes when said loopportions are of equal size and equal to one-half wavelength of saidlowest frequency.
 7. A broadband transmit/receive antenna as set forthin claim 5, in which said plurality of loop portions form a hollowtruncated cone having major and minor diameters, wherein said firstplane is disposed at the minor diameter of said truncated cone and saidsecond plane is disposed at the major diameter of said truncated cone,and wherein said plurality of loop portions comprise means defining anantenna directivity which is in a direction projecting outward from saidfirst plane.
 8. A broadband transmit/receive antenna as set forth inClaim 1, wherein said support means comprises a base member, aninsulative sleeve, first and second conductive sleeve portions fixed onsaid insulative sleeve in axially spaced-apart relationship, meansrotationally interconnecting said insulative sleeve with said basemember, conductive means for electrically interconnecting one end ofsaid antenna element to said first conductive sleeve portion and theother end of said element to said second conductive sleeve portion,first and second conductive terminals fixedly interconnected with saidbase member, an insulative tubular member fixed to said base member anddisposed coaxially within said insulative sleeve, first and secondconductive tubuLar members mounted in axially spaced-apart relationshipon said insulative tubular member and extending coaxially and in opposedfacing relationship with said first and second sleeve portions,respectively, and means connecting said first and second conductiveterminals to said first and second tubular members, respectively.
 9. Abroadband transmit/receive antenna as set forth in Claim 1; wherein saidsupport means comprises a base member having connected thereto said pairof terminals, an electrically insulated tube connected to and extendingoutwardly from said base member and having around the exterior thereof apair of peripherally extending and axially spaced-apart electricallyconductive portions, a support plate having means therein defining anopening through which said tube extends, means mounting said supportplate for rotational movement around said tube, a hollow membercoaxially disposed around and spaced from said tube and connected tosaid support plate to undergo rotational movement therewith around saidtube and having a pair of electrically conductive portions peripherallyextending thereover and axially spaced-apart therealong each in opposingspaced-apart relationship from respective ones of said electricallyconductive portions of said tube, and means electrically connecting saidtwo ends of said antenna element to respective ones of said electricallyconductive portions of said hollow member and electrically connectingsaid pair of terminals to respective ones of said electricallyconductive portions of said tube, whereby said antenna element may beangularly displaced to vary the antenna directivity.